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A: As you probably know, proper aeration with a deep water or shallow water aeration system is key to a healthy pond or lake. When water circulates and moves, oxygen flows throughout the water column, the water temperature is even, and the fish and wildlife thrive. You’ll see no stagnant areas or catch whiffs of bad odors. Instead, you’ll have a welcoming, enjoyable body of water, perfect for play and recreation.

If you think your aerator isn’t doing its job, it’s easy to diagnose: Just take your pond’s temperature!

The Tools

To begin, you’ll need a non-floating pond thermometer, a long string, a tape measure, a waterproof marker, a stopwatch, and a pad of paper and pencil. Tie the string to your thermometer, and measure and mark every 24 inches down the length of the string with your waterproof marker.

The Technique

Once your tools are set up, gather them together, hop in your boat and motor to various locations in your pond.

At each spot, noting where you are, drop the thermometer into the water and take the water’s temperature readings 24 inches down at a time, from the top to the bottom. Let the thermometer rest long enough (5 to 10 minutes) to get the true temperature reading at your desired depth.

Repeat this process in different areas (particularly if your lake is unevenly shaped), taking notes all along the way.

The Results

Once you’re done taking your lake’s temperature, look at your notes. Is there more than a few degrees difference in any of your temperature readings? If so, you’re more than likely under-aerating your pond.

The good news is that The Pond Guy® offers a free aerial mapping service. We’ll measure your pond and tell you where the diffusers should be placed so that you’re getting even aeration throughout the body of water. Take advantage of this free service! Your fish will thank you for it!

Q: How would I know if my pond has sufficient aeration? What would happen if my pond was “under” aerated? – Joe of Michigan

A: The best way to test to see if your pond is sufficiently aerated is by taking the temperature of the water one foot below the pond’s surface as well as the bottom. If there is a difference of more than 3 degrees Fahrenheit, then the pond is not sufficiently aerated and you may need to add additional diffusers or relocate the diffuser that you have.

Next, to answer the, “What would happen if my pond was “under” aerated?” question, lets compare a pond with no aeration, a pond that is under aerated and a pond with sufficient aeration.

A Pond with No Aeration: With no aeration present, the water is stratified (aka has a thermocline). Meaning that the water at the top is warmer and full of oxygen while on the bottom the water is cooler, nutrient rich and contains no oxygen. This causes the fish to habitat towards the surface of the pond. As the seasons change from the hot summer to cold winter, the pond goes through a process known as “turnover”. This is when the cooler water at the bottom of the pond, mixes with the warmer water at the pond’s surface. Since the rising cooler water contains no oxygen, the chances of a fish kill are imminent.

A Pond that is Under Aerated: When a pond is under aerated, the thermocline is not eliminated, only dropped further down towards the pond’s bottom. This can cause constant problems. As the bottom bubbler aerates, the bottom, nutrient rich water is lifted to the pond’s surface. These nutrients are now constantly available for algae to grow. More importantly, the water that is being lifted by the bubbler also contains no oxygen, thus increasing the possibility of creating turnover and killing the fish.

A Pond with Sufficient Aeration: You may ask, “Since the nutrients are still being brought to the surface, won’t an algae bloom and turnover still happen even if a pond is properly aerated?”

When an Aeration System is initially installed, it should be started at a slow pace to prevent creating turnover (See blog “When & How to Start Your Aeration System” for more information). As for algae, initially, when the nutrients are pushed towards the surface, algae will have the chance to bloom. As time progresses, however, the thermocline will be eliminated, the nutrients will be flushed out and the fish may now habitat the whole body of water.